1. Field of the Invention
The present invention relates to a surface emitting laser device, a surface emitting laser array, an optical scanning device, an image forming apparatus, and a method of manufacturing the surface emitting laser device. More particularly, the present invention relates to a surface emitting laser device and a surface emitting laser array capable of emitting light in the direction orthogonal to their substrate, an optical scanning device including the surface emitting laser device or the surface emitting laser array, an image forming apparatus having the optical scanning device, and a method of manufacturing the surface emitting laser device capable of emitting light in the direction orthogonal to its substrate.
2. Description of the Related Art
A Vertical Cavity Surface Emitting Laser (hereinafter may be referred to as “VCSEL”) is capable of emitting light in the direction orthogonal to its substrate. When compared with edge emitting semiconductor lasers capable of emitting light in the direction parallel to its substrate, the VCSEL may have some advantages such as lower cost, lower energy consumption, smaller size, preferable to two-dimensionally integrated devices, and higher performance. Recently, because of those advantages, the VCSEL has attracted increased attention.
The application fields of the surface emitting laser device include a light source (oscillation wavelength: 780 nm band) for an optical writing system in a printer, a writing light source (oscillation wavelength: 780 nm band and 850 nm band) in an optical disk apparatus, and a light source (oscillation wavelength: 1.3 μm band and 1.5 μm band) in a light transmission system such as an LAN (Local Area Network) using optical fibers. Further, a surface emitting laser device is expected to be used as a light source for optical transmissions between boards, within a board, between chips in a Large Scale Integrated Circuit (LSI), and within a chip in the LSI.
In those application fields, there are many demands for higher reliability and resistance to corrosion against moisture and the like.
In the surface emitting laser devices, however, a material including Al (e.g., AlGaAs) is generally used. Further, generally, plural surface emitting laser devices are simultaneously formed on a single substrate first. Then, the plural surface emitting laser devices on the substrate is cut into plural surface emitting laser devices. In this case, a cross-sectional surface of the material including Al may be exposed (see, for example, Nobuaki UEKI and four other authors, “Application of VCSEL array to a laser printer”, Electronics Society Congress of the Institute of Electronics, Information and Communication Engineers (IEICE), CS-3-4, S-31, 2004, and Japanese Patent Application Publication No. 2002-299761).
When a material including Al is exposed as described above, the material including Al may react with moisture or the like. As a result, the chip including the material may be corroded and may not be functioned as a semiconductor device.
To resolve the problem, there have been proposed methods of passivating an Al-containing material that is exposed on the side surface (see, for example, Japanese Patent Application Publication Nos. 2000-208811 and 2004-535057), and there has been another method of forming a protection film on the surface of the Al-containing material that is exposed on the side surface (see, for example, Japanese Patent Application Publication No. 2007-173513).
However, after the passivation or the forming the protection film, there is, for example, a dicing process or a scribe breaking process. Due to impact during such processes, a crack may be generated in the passivation film or the protection film. As a result, sufficient reliability may be impacted.